Chuck Bednar for redOrbit.com – Your Universe Online
Samples obtained by the Mars Rover Curiosity during recent drilling activity appear to indicate that acidic conditions were once present in the region of the Red Planet known as Mount Sharp, officials from NASA’s Jet Propulsion Laboratory revealed on Thursday.
While using a new, lower-percussion drilling technique to collect sample powder from a target known as “Mojave 2” last week, Curiosity uncovered evidence of water far more acidic than any detected to date, scientists at the US space agency’s Pasadena-based facility explained.
Partial analysis of the samples using the rover’s internal Chemistry and Mineralogy (CheMin) instrument has revealed the presence an oxidized mineral called jarosite. Jarosite contains iron and sulfur, and according to CNET, the sulfate typically forms in acidic environments.
CheMin Deputy Principal Investigator David Vaniman from the Planetary Science Institute in Arizona, said that his team’s initial assessment of the new samples indicated that they contained “much more jarosite” than similar specimens collected from the base layer of the mountain, at a target known as “Confidence Hills,” back in September 2014.
Curiosity, which arrived at the base of Mount Sharp five months ago after it spent the previous two years studying other locations within Gale Crater, has also delivered powder from Mojave 2 to the internal Sample Analysis at Mars (SAM) suite of instruments for chemical analysis. The rover may explore one or more additional sampling location in the area before moving on.
If the samples are confirmed to be evidence of the existence of more acidic water on ancient Mars, it will still have to be determined if that water was part of environmental conditions when the sediments that formed the Mount Sharp were initially deposited, or if they came later.
A license to drill
Upon the rover’s arrival at an outcrop known as “Pahrump Hills,” the Curiosity mission team had it drill two targets, Mojave and Mojave 2, to obtain samples for analysis. The first of those sites, Mojave, was selected because slender features that were smaller than grains of rice were visible on its surface. NASA wanted to see if those were salt-mineral crystals.
Unfortunately, the Mojave target broke during a drilling test, making it impossible for samples to be collected there. An alternate target, Mojave 2, was selected since it had similar crystal-shaped features. While the preliminary CheMin data from the drilled samples did not identify an obvious candidate mineral for these features, it is possible that the substances that formed them may have eventually been replaced by other minerals in later on in wet environmental conditions.
The drilling that led to the discovery of these samples might not have happened had the Curiosity scientists not recently decided to use low-percussion drilling technique for the first time on Mars, according to JPL’s John Michael Morookian, the mission’s surface science and sampling activity lead for the for the Pahrump Hills campaign.
“This was our first use of low-percussion drilling on Mars, designed to reduce the energy we impart to the rock. Curiosity’s drill is essentially a hammer and chisel, and this gives us a way not to hammer as hard,” explained Morookian.
The drill has six percussion-level settings which cover a wide range of activity, from gentle tapping to aggressive pounding, at a rate of 30 times per second, according to NASA. The low-percussion technique was tested and validated due to concerns over the fragility some of the more finely layered rocks near Mount Sharp.
The drill monitors how quickly or slowly it is penetrating the rock, and it automatically adjusts its percussion levels, the agency added. Sample-collection drilling activities at the sites that came before Mojave 2 all started at level four, and used an algorithm that was likely to remain at that same level. However, the new algorithm starts at level one, shifting to a higher level only if the drilling process is too slow, in order to prevent causing damage to the rock being drilled.
Curiosity returned to action late last month following a software update, conducting a mini-drill test at Mojave 2 to make sure that it was suitable for full-depth drilling. Mojave 2 is the fifth site from which rock samples have been collected by the rover during its time on Mars.
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